Quicktime resize problem

I noticed that when resize the jit.window to full screen it suddenly eats twice as much CPU than when the window is at original resolution, and the video also starts having problems refreshing.
It seams to be problem of Quicktime as the same thing happens if I play a video clip in Quictitime player and resize it. But if I play an AVI clip in Windows media player, or any other media player the difference between CPU usage at original resolution and full screen is really small,a and video runs totally smooth.

using Windows XP SP1, Quicktime 7.2., ATI Mobility Radeon X600.

I’m new to Jitter… so I might be doing something wrong, or is this normal, and Quicktime on windows is just so CPU demanding?